1. Field of the Invention
The present invention generally relates to a method and an apparatus for drying semiconductor wafers, and more particularly relates to a method and an apparatus for drying semiconductor wafers by using an IPA (isopropyl alcohol) drying apparatus.
2. Description of the Prior Art
Recently, IPA dryers have been used for the drying of semiconductor wafers, because, compared to a spin dryer, the semiconductor wafers incur less mechanical damage and a cleaner semiconductor wafer surface is obtainable.
A typical IPA drying apparatus is shown in FIG. 1. An IPA drying apparatus has an IPA dryer tank 100 to isolate the semiconductor wafers to reduce the water content contained in the semiconductor wafers. A plurality of semiconductor wafers 110, for example which have been washed after a wet etching step for example, are delivered by a mechanical arm to the IPA dryer tank 100 for drying and are supported by a holder 110. An IPA solution 120 is contained in the IPA dryer tank 100 and is heated by a heater 114 to its boiling point to generate an IPA vapor 122 in the IPA dryer tank 100. There are cooling or condensation coils 130 surrounding and disposed on the inner peripheral surface of the IPA dryer tank 100.
The IPA vapor 122 coats on semiconductor wafers 110 and combined with water thereon to become an IPA co-solution. When semiconductor wafers 110 rise to the level of cooling coils 130, the IPA co-solution is evaporated and water is removed from semiconductor wafers 110 at the same time. The IPA dryer tank 100 comprises a collecting tray 132 below cooling coils 130 which is mounted on the inner peripheral surface of the IPA dryer tank 100, to collect drips from cooling coils 130 and drain out from an outlet 134. The IPA dryer tank 100 further comprises an outlet 136 to exhaust the IPA vapor 122.
However, the IPA vapor 122 is continuously generated in the IPA dryer tank 100, and the IPA vapor 122 is continuously coating on semiconductor wafers 110. The disadvantage of the current IPA drying apparatus is that the continuously generated IPA vapor may contaminate dried semiconductor wafers again. Furthermore, the continuously generated IPA vapor causes production costs to increase.
The primary object of the invention is to provide a method for drying semiconductor wafers using an IPA drying apparatus.
Another object of the invention is to provide an apparatus for drying semiconductor wafers.
A further object of the invention is to easily control the input amount of the IPA vapor and increase the safety of the process.
In order to achieve the previous objects of the invention, a method comprising the following essential steps is provided. First, a solution is evaporated to generate a vapor, wherein the solution can generate a co-solution with water and the co-solution can evaporate at a temperature lower than 100. Then, a dryer tank is provided. Next, the vapor is piped to a porous hollow plate in the dryer tank. Last, at least one wafer is dried in the dryer tank, wherein the vapor is evenly diffused from the hollow porous plate.
Another embodiment is an apparatus for drying semiconductor wafers and the apparatus comprises the following elements. First, a vapor generator is used to generate a vapor. Second, a pipe is used to transfer the vapor, wherein one side of the pipe is connected to the vapor generator. Third, a dryer tank is used for drying wafers, wherein a porous hollow plate is on a bottom of the dryer tank and is connected to another side of the pipe. The porous hollow plate has a porous surface faced up in the dryer tank and the vapor is evenly diffused from the porous surface.